The value of a horse is often determined by the soundness of the animal's physical structure which requires the person evaluating an animal to make certain observations such as checking the animal's teeth, eyes, coat, hooves and overall general shape. These visual cues give some indication as to the animal's condition; however, they provide little indication of the horse's ability to perform or its locomotor ability. Often horses can have a condition or weakness that can result in lameness. As early as 1850 a flexion test was being used as a clinical tool to diagnose a horse's limbs for lameness.
This flexion test requires a clinician to apply a force on a limb held in a flexed position for one minute, in some cases the test is conducted over a one and a half minute period. The horse is then trotted off to observe lameness.
Many in the field of equine evaluations such as horse trainers and veterinarians have determined this method of evaluating a horse for lameness is very subjective. The ability of the person conducting a flexion test varies depending on the strength of the person, the ability to apply a uniform force on the flexed limb and on experience. Typically an experienced adult male conducting the flexion test applies an average force of 150 Newtons with a variation of slightly greater than 10% during a test. And even more significantly, the average applied force can vary greatly, for example during a single test the average force instead of being 150 Newtons can vary between 100 and 175 Newtons. Females generally apply a mean force of 110 Newtons in a report published in 1997 by P. R. Keg et al entitled “Variations in the force applied to flexion tests of the distal limb of horses” published in Veterinary Record (1997) 141, 435-438.
This study acknowledges the variations in the test were so great that one could not rely on the test as a tool for evaluating a horse for lameness. The same horse may pass the test if the force applied was well below the average 150 Newtons, but the animal would show lameness if the higher force of 150 was maintained over the full minute duration.
As a result, the study showed the flexion test was critically flawed. The study used a prototype device to measure or quantity the force applied referred to as a flexometer.
The flexometer device was a cumbersome piece of equipment. A force transducer was designed which consisted of a rounded polyvinylchloride plate, with about the same curvature as the hoof of an adult horse, to which an air-filled rubber tube was fixed. The air pressure within the tube is measured by an electronic manometer at the outlet of the tube, the signal from which was pre-amplified in a charge amplifier. The output signal was visualized on a numerical display, and can be fed to a chart recorder. The device was calibrated by applying a known force to the device while simultaneously recording the output and measuring the actual force (in Newtons) by means of a steelyard.
A line extended approximately 8 to 10 feet from the curved plate with the rubber tube lining the plate to the meter which in turn was connected by another line to a chart. The person conducting the test needed to observe the force readings on the meter while holding the horse and not getting entangled in the lines. This device worked adequately in a controlled test environment as several persons were actively involved, one holding the horse, one monitoring the chart and the test performance and one actually conducting the test. The problems of using such a device on a non-experimental basis are numerous.
The person conducting the test may or may not have one or more assistants, the horse may or may not stand still and avoid getting entangled in the numerous lines, the access to a/c power outlets may not exist at the location where the animal is to be tested and the ability to read a digital display can be affected by the distance the operator is located from it and the amount of sun glare if the test is conducted outside. These are just a few examples of the problems associated with this prototype device.
The present invention had as an objective to provide a greatly improved device that was capable of making the flexion tests not only much more uniform and therefore reliable, out actually made conducting this important test easy to perform.
A further objective was to make a device suitable for a wide range of horse hoof sizes.
Another objective was to improve the design to make it a portable self contained device free of all line connections during the actual test and made so all force measurements were stored in the device itself so the operator's attention and focus was always on the animal being evaluated.
These and other objectives are achieved by the present invention described as follows.